Tosoly: Biogas plus!

What another world! Tosoly is the farm and biogas demonstration site I wrote about before, where I just ended a week’s work-study to learn as much as I could from Lylian Rodriguez and her husband Ricardo about this technology. Lylian has a doctorate in Sustainable Production of Renewable Energy in the Tropics and has worked in VietNam, Cambodia, Costa Rica and now, for 20 years, in Guapota. She has 30 years’ experience with biodigesters and has had nine of them on their farm here. These digesters can last for 14 years or longer. Currently seven are working; one is languishing for lack of visitors (and their poop). Lylian helped form Redbiocol (Network of Biomass in Colombia) 12 years ago, and has personally been part of building 553 digesters. She also works for the University of Tropical Agriculture (UTA). Their website,, has many videos and other resources on biogas, mainly in Spanish. I paid $200 US for my room, board, and learning.


On the exterior of the buildings there are many methane tubes and water pipes going every which way, but inside their home it’s delightfully decorated with paintings from VietNam and Cambodia on the walls, a highly functional kitchen, and a fabric sculpture in progress. They built the whole house, animal stalls and guest house themselves; all the plumbing of greywater and black water goes to various biodigesters. The extra-wide diameter bamboo-like plant which grows rapidly here is part of the furniture in many areas of the house and the cabin.

Nearly all of the lighting comes from a few solar panels. There is a grid inter-tie for one of these, others are connected to batteries. They also have solar-heated water for showering. Apparently, the warm water from the shower boosts the temperature of the digester that receives it, giving good methane production.

There are at least three open ponds, plus 4 large water cisterns.

Then there are what I call the “blimps”: 3-meter greenhouse plastic reservoirs hanging overhead, under roofs, that are connected to the digesters via half-inch tubing. One can eyeball the amount of gas available, and cinch them around the middle to increase the gas pressure.

Not everyone uses these, but Lylian has five and swears by them. Each 3-meter reservoir can hold an impressive 3900 liters of gas, almost 4 cubic meters. 2 cubic meters of biogas = 1 pound of LPG (liquid propane gas).

My little cabaña was charming! I was the only guest. There are rooms that sleep up to 8 people; mine had a bunkbed, shelves, a desk, and bathroom with cold shower. The kitchen has a biogas-powered stove, of course! On one wall is a beautiful brightly colored mural depicting a coffee plant and delivery of delicious coffee to a city. Their brand of biogas-roasted coffee is Lo Bueno del Monte.

There are several plastic greenhouses here. One is devoted to drying coffee beans (and laundry). One is almost all tomato plants. Another one is full of green bean vines, and I picked a big fistful. There are also some fields growing corn and 2 varieties of kale, I also saw some basil, arugula and lettuce. This field has an overhead irrigation device.

Down a major hill, most of the coffee is grown, under partial shade provided by plantain trees. Unfortunately, ants eat a lot of the coffee leaves. Playfully, Lylian picked up a giant cone from the bark of the plantain and put it on her head, so I called her the “Buena bruja de biogas!” (Good witch of biogas)


I was so excited to be learning the biogas operation! I followed Ricardo around as he scraped up pig poop and deposited it in a channel into which he poured buckets of water to flush it down to the biodigester. With a tape measure, I measured five of the biodigesters’ length and width. I removed, cleaned and replaced the plastic water bottles that act as safety valves. (They fill with algae.) My boots came in handy for that job. When cleaning the plastic bottles, the valves are closed, and as a safety measure the open tube is capped with a plastic bag and a piece of bicycle tire like a rubber band.

I calculated the area of five digesters to know how much their capacity is. Lylian had me measuring the amount of water I used to wash the dishes at breakfast and lunch (about 5–6 liters each time). This is part of the greywater that enters the system. After measuring the length of each digester, I figured the volume. They’re all about the same depth, 1 meter, and width except for the geomembrane one (heavier, more expensive material which lasts longer, a bit less wide than greenhouse plastic tubes). Grand total: 26,760 liters!

A family of 4 might use 60 liters a day on toilet flushes, 30 or more liters for showers and hand washing, 20 or more liters washing vegetables and dishes in the kitchen, and an average of 6 liters a day on washing clothes. That adds up: easily 120 liters a day of greywater and blackwater alone. The rule to remember is that for 40 kilos of fresh animal manure a day, around 120 liters of water should be added (3 times as much), which could be greywater, blackwater and/or rainwater.

I learned that the effluent of the biodigesters, mixed with biochar and minerals, increases the yield of production by up to 500%. Biological proofs with seeds of corn show that after 40 days with treatment, the root systems are more developed and the plants are stronger, with a bigger diameter and taller than in the control group.

Lylian says that the digesters that include human waste go through a double treatment by having the effluent flow to a second digester and then into the 60,000 liter biodigester that continues the process. This one is not for producing gas, but there is still anaerobic microbial activity reducing pathogens. There are hoses connecting this digester to the area downhill where most of the coffee is grown. Universidad Libre has a test for E Coli. The final effluent has come back within acceptable limits.

I had noticed that one of the outlet tubes for a biogas digester looked clogged, and Lylian reamed it out with a length of black hose. A large amount of effluent immediately spilled out into a small square box from whence it flowed downhill to the 60,000 liter digester. A lot of underground pipes are involved.

She took samples from a couple of the digesters’ effluents and placed some duckweed into each. The duckweed had been growing on water that wasn’t enriched. Within two days, the pallid duckweed became deeper green! The next project we began was to improve and enlarge a small pond that had sprung a leak, to add a better liner and begin to grow more duckweed there. I learned that in two bigger ponds, there are tilapia and a type of carp. These fishes’ growth is enhanced by adding effluent to the ponds, and they also eat duckweed. It is 25% protein, very easy to grow, making it an ideal dietary supplement for fish, ducks and chickens.

In the large classroom attached to the main house, Lylian got out a life-size model for me to learn from: a 3-meter, double bag of greenhouse plastic that had 4-inch tubes attached at each end. She closed off the ends with plastic bags, and filled it with a blower. She showed me how the intake and outflow tubes should be positioned at about a 45 degree angle, with the bottom of the tube about 50 cm from the bottom of the bag. At the top of the big bag, an airtight connection is made with half-inch PVC pipe, nipple adaptors and rubber washers for the methane gas to travel through. It really is a simple device. The bottom 80% will be filled with liquid and manure, while the top 20% will hold the gas.

Daily life on the farm

Such kind and lovely folks! Lylian made delicious meals for us daily, all cooked on the biogas stove. A typical breakfast could be a fried or boiled egg laid by their hens, toast with butter and mora (blackberry) jam, a mix of tropical fruits, some oatmeal and delicious fresh coffee roasted with biogas. Over a late lunch featuring lentils, Lylian pointed out that the lentils are imported from Canada and contain chemicals like pesticides, whereas the chicken that they eat is protein locally grown on the farm with much less negative impact on the planet! Gave this vegetarian something to ponder.

Ricardo is always out early feeding the animals, with no days off. So much energy! In one day, he will mix biochar with minerals, plant 30 tomato plants and 20 coffee plants, do some pruning, harvest plantains and fruits, harvest fodder, feed the animals, shovel manure, lay down fresh bedding (bagasse from pressing sugar cane) for the sow and her piglets, and much more.

Two young men who are neighbors help out a few days a week on the farm: Jesus and Angel. One woman, Luz Blanca (White Light), does some housework and a little cooking.

My tasks were rather mundane: preparing some of the breakfast, washing dishes, cleaning out the safety valve bottles, helping feed animals, and one day I bagged up two large sacks (about 80 kilos) of coffee, dried in a large greenhouse, to bring into San Gil for sale.

The goats are endlessly entertaining. They beg loudly to be fed, and it’s fun to bring them any type of prunings and weeds and watch them devour it.

The mule is such a patient creature. Ricardo invited an old campesino to demonstrate the ancient way of loading up a mule with firewood and bags of goods, so that Ricardo could make a video. The mule stood calmly as at least 200 pounds were skillfully strapped on her back. I rubbed her face and neck and she nuzzled my pant legs.

Some consternation: apparently the big dog accidentally knocked over one of the support structures for the biogas-containing tubing near the house, and some gas escaped. No explosion, everything is low pressure.


The costs for materials for building a digester at Paul’s are higher than I had thought. We’ll need almost a full roll of greenhouse plastic, 50 meters, which costs around $250 US, in order to create two 8-meter double-walled digesters and two gas storage reservoirs; plus lots of PVC tubes and pipes and rubber and accessories and shade cloth, which together could easily cost another $200 US. The special stove ($70 US) and a device to increase the pressure add more costs, although one can fairly easily modify a standard propane stove to run on biogas. Labor costs for digging the trench and canals for pipes for greywater, blackwater, and animal manure will also add up. Biogas digesters reportedly pay for themselves in about a year and a half, according to some literature Lylian showed me. The $1000 contribution from my fundraising last year will only cover the roll of greenhouse plastic, plus site visits to some digesters that have problems, planning for Paul’s digester, teaching, construction, and at least one follow-up visit. Paúl will be picking up the tab for the rest of the materials and labor.



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Cathy Holt

Cathy Holt

Cathy is a member of the Earth Regenerators Network. She’s passionate about regenerating landscapes with water retention, agro-forestry, and biogas digestors.